The report found 55% of employers expect to increase long-term overseas assignments and highlighted for the last two years there has been an increase in the overall number of international assignments.
It found China, United States, Brazil, UK and Australia are the priority destinations in their respective regions for expatriates.
Mercer's Worldwide International Assignments Policies and Practices report (WIAPP), also showed more than half of employers reported an increase of long-term (52%) and short-term assignments (53%) in 2011 and 2012.
According to the report, the top five reasons cited for international assignment programmes are: to provide specific technical skills not available locally (47%), to provide career management/leadership development (43%), to ensure knowledge transfer (41%), to fulfil specific project needs (39%) and to provide specific managerial skills not available locally (38%).
The report also looked into gender differences of employees on assignments and found the likelihood of expatriates being female has marginally increased, with the average percentage of female assignees standing at 13%, just 3% higher than two years ago.
Major obstacles to employee mobility includes family-related issues, such as concerns over children's education and spouses not wanting to compromise their own lives.
"Career management" ranks as the next most important issue, except for European and Asia Pacific companies, which rate lack of "package attractiveness" as the second-biggest obstacle to mobility.
Anne Rossier-Renaud, principal in Mercer's global mobility business said: "International assignments have become diverse in order to meet evolving business and global workforce needs.
"Relatively low pay increases in some regions and pressure on companies to attract and retain talent, have spurred many to embrace a wider range of global mobility strategies to incentivise high performers."
She added: "Mobility and HR directors now face great complexity in the number and type of international assignments that need managing."
